[R] recursively divide a value to get a sequence

[Wacek Kusnierczyk]

two alternative solutions with a more functional-style taste:

dilute = function(init, div, count)
    sapply(1:count, function(i) init/div^(i-1))

dilute = function(init, div, count)
    if (count == 1) init
    else c(init, dilute(init/div, div, count-1))

vQ



René Capell wrote:
> Hi Anne-Marie,
>
> maybe its not particularly elegant, but this function does the trick:
>
>   
>> dilute<-function(val,div,len){
>>     
> +   res<-rep(val,len)
> +   res<-res/div^c(0:(len-1))
> +   res[len]<-0
> +   res
> +   }
>   
>> dilute(15000,5,9)
>>     
>
> Cheers, René
>
>
>
>   
>> -----Ursprüngliche Nachricht-----
>> Von: "Anne-Marie Ternes" <amternes at gmail.com>
>> Gesendet: 09.07.08 14:12:16
>> An: r-help at r-project.org
>> Betreff: [R] recursively divide a value to get a sequence
>>     
>
>
>   
>> Hi,
>>
>> if given the value of, say, 15000, I would like to be able to divide
>> that value recursively by, say, 5, and to get a vector of a determined
>> length, say 9, the last value being (set to) zero- i.e. like this:
>>
>> 15000 3000 600 120 24 4.8 0.96 0.192 0
>>
>> These are in fact concentration values from an experiment. For my
>> script, I get only the starting value (here 15000), and the factor by
>> which concentration is divided for each well, the last one having, by
>> definition, no antagonist at all.
>>
>> I have tried to use "seq", but it can "only" do positive or negative
>> increment. I didn't either find a way with "rep", "sweep" etc. These
>> function normally start from an existing vector, which is not the case
>> here, I have only got a single value to start with.
>>
>> I suppose I could do something "loopy", but I'm sure there is a better
>> way to do it.
>>
>> Thanks a lot for your help, hope the question is not too dumb...
>>
>> Anne-Marie
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>     
>
>
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> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   


-- 
-------------------------------------------------------------------------------
Wacek Kusnierczyk, MD PhD

Email: waku at idi.ntnu.no
Phone: +47 73591875, +47 72574609

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